This invention relates to the art of tube expanding tools and, more particularly, to improvements in connection with a tube expanding tool of the type in which radially expandable jaws mounted on the tool body are displaced radially outwardly by movement of a coaxial drift pin in one direction relative thereto and are displaced relatively inwardly by a jaw biasing spring upon displacement of the drift pin in the opposite direction.
It is well known to provide a tube expanding tool of the character comprising a body supporting fixed and pivotal handles and tube expanding jaws which are displaced radially outwardly by means of a tapered pin which is displaced in a jaw expanding direction by means on a cam on the pivotal handle. The jaws are spring biased radially inwardly against the tapered pin to promote retraction of the pin from the jaws following a tube expanding operation and removal of the camming force against the pin. The tools disclosed in U.S. Pat. Nos. 3,550,424 to Rast; 4,043,171 to Brookman; and, 4,425,783 to Rast are exemplitive of such tube expanding tools.
In use of tools of the foregoing character, the jaws of the tool are introduced into the open end of a tube, and the pivotal handle is pivoted to displace the drift pin to expand the jaws against the inside of the tube end so as to enlarge the diameter thereof. As exemplified by the Rast and Brookman patents identified above, such previous tools have achieved the jaw expanding pin displacement by providing the pivotal handle with a cam adjacent the pivot axis thereof and which cam is cooperable with the tail end of the drift pin, or an extension thereof, to impose a lever force axially against the pin. Further in connection with accommodating manipulation of the pivotal handle by the user of the tool, it is desirable to require a pivotal displacement of the handle of no more than about 90.degree.. In this respect, manipulation of the pivotal lever at the outset of a tube expanding operation becomes progressively more awkward and cumbersome for the user as the initial relative positioning between the fixed and pivotal handles exceeds about 90.degree.. However, as will be seen from U.S. Pat. No. 4,425,783 to Rast mentioned above, angular displacement of the pivotal cam handle considerably greater than 90.degree. is required in connection with the prior cam handle arrangements to obtain the desired tube expanding pin stroke with a single displacement of the pivotal handle. Efforts heretofore to obtain the necessary pin stroke with a pivotal displacement of the cam handle of about 90.degree. has resulted in arrangements such as that shown in U.S. Pat. No. 3,550,424 to Rast mentioned above wherein the pivot axis of the pivotal handle has plural axial positions relative to the tool body to enable obtaining the desired total pin stroke by two successive manipulations of the pivotal handle, each with the pivot axis of the handle in a different one of the two positions thereof.
While cam handle arrangements of the foregoing character have provided the intended directional application of force to the drift pin, they have resulted in structural complexity, and they are cumbersome to operate either as a result of the initial angular relationship between the fixed and pivotal handles or the requirement for multiple operation to achieve a desired total stroke for the drift pin. Moreover, the sliding frictional engagement between the cam and pin and transverse to the pin axis imposes side thrust on the pin, thereby ofsetting the advantage of axial force application between the cam and pin. Furthermore, the structural complexity and/or the use of slidably engaging cam and follower surfaces undesirably adds to the cost of manufacture of the tools in that the interengaging surfaces must be precisely contoured to promote the rolling engagement therebetween as in U.S. Pat. No. 4,425,783 and must be smoothly finished to minimize friction in connection with the sliding interengagement in arrangements such as that shown in U.S. Pat. Nos. 3,550,424 and 4,043,171.
In addition to the foregoing disadvantages, the cam handle type tube expanding tools heretofore provided have relied on a garter-type spring arrangement for promoting retraction of the drift pin from between the expandable jaws and contraction of the jaws following the tube expanding operation. More particularly in this respect, the tapered end of the drift pin engages correspondingly tapered radially inner surfaces on the jaws, whereby forward movement of the drift pin in the tool body displaces the jaws radially outwardly to achieve the expansion of a tube in which the jaws are disposed. Following such tube expansion, the pivotal handle is returned toward its initial position and a garter spring surrounding the jaws provides a radially inwardly directed force thereagainst which tends to promote displacement of the tapered pin toward its initial rearward position relative to the jaws.
A considerable number of problems have been encountered in connection with use of these tools which result in damage to the tool and thus undesirably high maintenance and/or replacement costs, the damage of tubing being worked on, and frustration for the tool user. In this respect, even when such tools are new, it is often necessary to jiggle the tool relative to the tube following a tube expanding operation in order to induce initial rearward displacement of the drift pin sufficiently for the jaws to contract to enable removal of the jaws from the expanded tube. In connection with use of the tool for a period of time, the area between the drift pin and its bore and between the tapered end of the pin and the jaws becomes contaminated such as by the ingress of dirt, oil and the like. As a result of such contamination and/or through repeating sliding displacements of the pin relative to the body and jaws, the interengaging surfaces between the body, pin and jaws becomes scored. As a result of such contamination and/or scoring, the pin sticks in its forwardmost position following a tube expanding operation whereby it is difficult if not impossible to separate the tool from the expanded tube without damaging the latter and/or the tool jaws. Furthermore, such sticking of the pin requires at least initial physical displacement of the pin rearwardly of the jaws and tool body, such as by hitting the nose of the pin against a rigid surface such as a floor. Depending on the degree to which the pin is stuck, varying impacting forces are required to dislodge the pin. This eventually results in peening of the nose of the tapered portion of the pin and, more importantly, when the pin is dislodged the jaws impact against the rigid surface, causing damage and/or breakage of the jaw elements.
It will be appreciated that frequent disassembly of the tool and cleaning of the pin, body and jaw surfaces is necessitated in an effort to avoid sticking of the pin as a result of contamination and/or scoring of the tool element surfaces. It will be further appreciated that the latter results in undesirably high maintenance time and cost, and that any sticking of the pin which results in damage to an expanded tube by removal of the tool therefrom and/or damage to the pin or jaws of the tool by impacting the latter against a rigid surface likewise results in undesirably high maintenance and/or replacement costs.